Oscilloscope photographic system



March 31, 1953 1.. R. SPAULDING OSCILLOSCOPE PHOTOGRAPHIC SYSTEM Filed March 31, 1949 INVENTOR.

LYMAIV R. SPAULQ/NG' Patented Mar. 31, 1953 2,633,403 OSCILLOSCOPE PH OTOGRAPHIC SYSTEM Lyman R. Spaulding, Portland,-Oreg., .assignor to the United States of America as represented by the Secretary of the Interior Application March 31, 1949, Serial No. 84,665

6 Claims. (01. 346--110) (Granted under Title 35, U. S. Code (1952),

see. 266) e The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment to me of any royalty thereon in accordance with the provisions of the act of April 30, 1928 (Ch. 460, 45 Stat. L. 467).

This invention is concerned with the photography of the images appearing on the screens of cathode ray oscilloscopes together with the photographing of a timing indicator. Cathode ray oscilloscopes produce a screen image lasting only a short time. In some applications of these instrument the image may occur only at unpredictable times thus requiring that the camera and the contained photographic film be left ready for exposure for indefinite periods usually of the order of an hour.

During these periods of waiting for an exposure, the oscilloscope tube produces a faint illumination directly from its cathode which passes through the screen and gradually fogs the film. This has been observed by others and as expedients to assure a reasonably unfogged film color selective filters have been used and the film has ben periodically changed to provide a new film after the preceding film has been appreciably exposed to the stray oscilloscope light.

The periodic replacement of film to circumvent the fogging is a nuisance and an expense which can be minimized by my invention. Accordingly a principal object of my present invention is to produce an oscillograph photographic system which will permit the exposure of film to the inactive oscilloscope screen a maximum length of time with a minimum of fogging.

In the photography of oscilloscope records it is usual to need a record of time photographed at the instant of occurrence of the photographed phenomenon. Means for fulfilling this requirement constitute a second object of this invention. Another object is to provide in connection with the time record, means for illuminating the time indicator momentarily for photography.

The photography of oscilloscopic images requires adjustment of the camera and the associated parts and means for observing the performance of the equipment. Hence, another object of this invention is to provide appropriate means for observing the oscilloscope screen during preparation for the photography.

What constitutes my present invention is described with reference to the accompanying drawing in the specification following and is succinctly defined in the appended claims.

-- In the drawing, Figure 1 is an external top view of a preferred form of embodiment of part of my invention. Figure 2 is a side elevational view, partly in section. Figure 3 is a perspective view of part of my invention showing in the normal relative locations, an oscilloscope screen and a time indicating instrument. Figure 4 shows, in schematic form, a circuit diagram of the electrical arrangement used for momentarily illuminating the time indicator.

In Figure 1 my invention comprises three cones I, 2, and 3, and a cylinder 4. At the front of the cones a fitting ring 5 is provided to adapt the assemblage to the front of the oscilloscope, of which the oscilloscope cathode-ray tube 6 is indicated in dotted lines. A clip I is provided for convenience in holding the assemblage in place on the oscilloscope. At the small end of cone I provision is made for mounting a camera 8, shown dotted.

The structural arrangement of cones I and 2 is such that they are concentric at the camera lens, and laterally separated at the plane of the oscilloscope screen. The two cones I and 2 are cut out along the two lines where they coincide so the camera lens has a view through the resulting slot to photograph the time indicator. This is shown in the cut-away portion of Figure 2, in which lines I! and I2 are the lines of coincidence of cones I and 2. The space between lines II and I2 is cut out and the two cones I and Z are fastened along these two lines as by welding or soldering.

Cones I and 3, as shown in Figures 1 and 2, are as described for cones land 2, joined along their line of coincidence. The portions of cones i and 3 within their common line are cut out so that cone 3 gives a view of the oscilloscope screen. At the apex of cone 3 there is a closure l3 which can be opened for visual inspection of the screen of oscilloscope tube 6.

Cylinder 4 is cut into cone 2 in a way analogous to the way cone 3 is cut into cone I. The purpose of cylinder t is to support and to enclose means for illuminating the time indicator in a housing I4. Cylinder 4 contains an electric lamp I5 preferably of a gaseous discharge type supported in a removable cap and socket I6.

The spacial arrangement of the oscilloscope tube 6 and the time indicating assemblage is shown in Figure 3. An oscilloscope screen I B with an illustrative oscilloscopic trace I1 is shown at the end of cone I. A clock I8 is shown in the housing I4. Cone I is placed to afiord a full view of screen I1 and cone 2 to afford a view of clock I8;

- flows throu h :resistor 26 and-lam I 5.

light from cathode 2| is not appreciably reflected, or scattered. Thus the lens of camera 8 being" below the line from cathode '2 I 'to' some $22 protected from unwanted exposure. At the same time, the lens of camera 8 has ai'ffill viewofiscreen I6 of cathode ray tube 6 and df'thetimerIIiB.

In the operation of the recording system, it is" necessary that lamp I5 beiilluminatedioniyforbrief periods at the approximate.time:.ofoceur-- rence of the oscilloscopic record I1. 'Thisinomentary illumination of lampiifii'israbcdmplisheii" by the circuit shown in Figure 4. Power for lamp l I5 is provided by a battery grounded at one ter- -:.=minal and connected to ;:thecircuit when :indi- :cated 'by .-B-+ :A :lrnaillast :Jresistor124 "is provided zior rcurrent limitation. A condenser :25 is confnected to provide "for :"current i surges r-exceeding %the momentary c'current zcapacity-of l the battery.

Condenser :25 is 'connected to 1 lamp I5 :througha purreritflimiting resiStor:2-6 ,I'and through another =path-in';parallel therewith including coil 27. Coil 21 is the actuating coil of :a solenoid :or "other electr c-mechanical :device :Icapable of operating acameraril oncelfor each operationof the oscillosc'zope li'andilamp= I5.

Thecir'euitis closed through a' gas-filled tetrode 18 'and a thermally :closed elec-trically ioperated :switch29. Switch 1915 heldinorm'ally closed: by current inza =;'coil :30, 'iprovided -'by the plate circuitco'f a triode 3 I llheigridtof -triode '3 I :is held :normally "at a "voltage which is approximately that of 25+ by a grid resistor 32 of highlresistzance. A v-ggrid :bias :resistor :33 :is i-prov-ided and econnectedt'o ;providera negative: grid voltage uni der :certain conditions.

i In the operationioiithesystem,-the-lcontrol 3grid' rof tetrode L128 "causes tetrode 28=to become conducting. A :surge of current from" condenser :25

The cur- .rent-through. resis'tor 26, gradually; but in-afraction of-"a second; decreaseswith a corresponding \increase-incurrent1incoi121. Lamp I5 thus is illuminated only-foralength7of=timecorrespond- :ingto the time-constant of-the circuitcontaining coil 2'1. When tetrode 28 becomes conducting :theivolta'geqon the plate: thereofffalls: quickly 'to a ".vaIueImuch less thankB+. I This-decreased "voltage is less EthaniG- LSO :the grid: of trioderii I becomesssufiicientlytinegative to decreasethe plate zcurrentithereofgfiowingrthroughlcoili3iletorazcom- -iparativly small value. When this occurs, :the :contacts "of norm-allyaclosed switch iii-open res'torin tetrode'28 to a normallyv-high impedance.

condition.

.The surge o'f curren't 'throug'hcoil 21 .operates "camera-18 :Thisoperation-advances the exposed irameo'f 'film in camera 8 bringing a a new frame The -.of film .into (position "for lthetnext exposure. .shutteixdf "camera-8 is .locked lopen manually/at all times except whencamera .;8 .is to" beremoved fromcone I. .The operation o'frthe .circuitrshown in Fig. 54 excites f lamp I-I5,.1illuminating clock .I B

; momentarily rafter the-occurrence of a transient 1 intoscilloscopefirapable; of...initiating operation of tetrode v 28. i'I'hismperation ifollows the-exposure {Lof 'itheitransientiinlioscilloscope G1 by{a;smallifrac- :=.tion-;off i-arsecond. :The etransients eintoscilloscope for whichthis system is usually used ejoccurzin.

4 single non-repetitive sweeps of the cathode ray. This makes the use of the shutter in camera 8 unnecessary in normal operation. Thus it will be understood that the operation of camera 8 is rthatoftadvancing the filmtonaframerather than ftha't'o'f operating'theconventionalrshutter. It is this characteristic of operation that requires the arrangement of cone I to prevent fogging the film when the length of time between successive 10 wperationszisiappreciable.

It will be apparent that some of the elements of :my 'present "invention have utility for individualcuse. However, the invention as a whole is :req'uire'dto operate the photographic system for 15 .therbestztre'suit's; :According1y I claim:

l In ..combination, an oscilloscope having an axis'on which is a cathode which glows when op- 5erating,zand:a.a-view screen, a camera having an reoptical axis, said camera being placed on the side of said view screen opposite said cathode, a light-tight hood .Iconnecting .the cameral-and :said 'view;screen,esaidaoscilloscope axi sIahd-theoptical axeeref:saidtcameraemaking suchaan obtuse angle l-that the ;camera .does not. have a direct view-..of

'.-.the cathode through :the view screen.

I 2. The combination :of .claim 1, in which the light tigh-t hood has :a conicalshape and *has a light absorbing surface.

3. :Thezcombination or claim 1, in which the light-.tighhhood 21131-5: aconical shape :and a light absorbing :interior surface, -.the arrangement between :the parts being such that a line from=the cathode through the point of zthe'view-v-screen nearestthe camera strikesthe interior light absorbing surface of the hood.

: i. anoscilloscope photographicrsystem, i the combination of first and second=light-tight hoods each having :a small open tend-and a. large open end, leach of "said large open ends defining .the :perimeter 10f different plane afield .of View, vthe small open :ends of ..said first and second hoods EGIIIgCOIICGIItIlC and having an unimpeded view of both fields of viewdefined-by the open .ends of said firs-tend secondhoo'ds, the-overlappingporarranged;to illuminate the afield of :view defined by" the large endro'f;v said second: hood, the axes :of asaldi first, second, thir'dand-ifourthhoo'dsimaking ;lacute ang1es with-.eacheother, theaxis Iof. said-first .cone making aha-angle withthe, plane field of view defined by the large endof saidfirstcone.

I The combination of 'claim ilin which the first,-nsecond and third hoods are "substantially conical in. shapeanddn which-themfourth hood is substantiallycylindrical.

6. The =conlbination of claim \4 in which the ccmbihationlof hoods attached-tea camera with a lens. a clock v:anda cathode ray tubeihaving a :cathoderand .a viewing screen, vtheescreeneof .-the tube being substantially I in the'fieldof -.view defined .by. the1firsthood,theecamera lensbeingsat the concentric small openings :of the first fland secondchoods-and the-cathode beinglon atherside of saidscreen remoteirom saidtcamera-I ena-the ,angie between nthes'axiscof thelfirstihoodand the 'plane field view of.thelfirsthood-heingssuchzthat .ihe am ea smeth ei e imrqu cahe said screen of the said cathode, the clock being Number in the field of view of said second hood. 2,166,440 2,169,726 LYMAN R. SPAULDING. 2,186,268 5 2,200,095 REFERENCES CITED 2,406,152

The following references are of record in the file of this patent:

Number UNITED STATES PATENTS 10 473,043 Number Name Date 729,315

1,736,456 Matthias Nov. 19, 1929 2,160,006 Thompson et a1. May 30, 1939 Name Date Jones July 18, 1939 George Aug. 15, 1939 Pakala. Jan. 9, 1940 Marton May 7, 1940 Levine 1 Aug. 20, 1946 FOREIGN PATENTS Country Date Great Britain Oct. 5, 1937 France Apr. 25, 1932 

